METHOD AND APPARATUS FOR STORING COMPRESSED DATA FOR SUBSEQUENT PRESENTATION ON AN ACTIVE ADDRESSED DISPLAY

Abstract: An electronic device (55) for driving an active-addressed display (100) comprises a data port (505) for receiving image data and compression circuitry (530) coupled to the data port (505) for generating compressed data by compressing the image data using a method in which the image data is two-dimensionally transformed utilizing a plurality of orthonormal, i.e., orthogonal and normalized, functions. The electronic device (500) further comprises transforming circuitry (515) coupled to the compressing circuitry (530) for performing a one-dimensional transformation of the compressed data using the orthonormal functions to generate a set of column values. Column drivers (565) coupled to the transforming circuitry (515) and the active-addressed display (100) drive columns of the active-addressed display (100) with analog voltages corresponding to the set of column values.

Description: METHOD AND APPARATUS FOR STORING COMPRESSED DATA FOR SUBSEQUENT PRESENTATION ON AN ACTIVE ADDRESSED DISPLAY Field of the Invention This invention relates in general to data compression techniques, and more specifically to data compression in an active addressed display system. Background of the Invention An example of a direct multiplexed, rms (root mean square) responding electronic display is the well-known liquid crystal display (LCD). In such a display, a nematic liquid crystal material is positioned between two parallel glass plates having electrodes applied to each surface in contact with the liquid crystal material. The electrodes typically are arranged in vertical columns on one plate and horizontal rows on the other plate for driving a picture element (pixel) wherever a column and row electrode overlap. In rms-responding displays, the optical state of a pixel is substantially responsive to the square of the voltage applied to the pixel, i.e., the difference in the voltages applied to the electrodes on the opposite sides of the pixel. LCDs have an inherent time constant that characterizes the time required for the optical state of a pixel to return to an equilibrium state after the optical state has been modified by changing the voltage applied to the pixel. Recent technological advances have produced LCDs with time constants (approximately 16.7 milliseconds) approaching the frame period used in many video displays. Such a short time constant allows the LCD to respond quickly and is especially advantageous for depicting motion without noticeable smearing or flickering of the displayed image. Conventional direct multiplexed addressing methods for LCDs encounter a problem when the display time constant approaches the frame period. The problem occurs because conventional direςt multiplexed addressing methods subject each pixel to a short duration "selection" pulse once per frame. The voltage level of the selection pulse is typically 7-13 times higher than the rms voltages averaged over the frame period. The optical state of a pixel in an LCD having a short time constant tends to return towards an equilibrium state between selection pulses, resulting in lowered image contrast, because the human eye integrates the resultant brightness transients at a perceived intermediate level. In addition, the high level of the selection pulse can cause alignment instabilities in some types of LCDs. To overcome the above-described problems, an "active addressing" method for driving rms responding electronic displays has been developed. The active addressing method continuously drives the row electrodes with signals comprising a train of periodic pulses having a common period T corresponding to the frame period. The row signals are independent of the image to be displayed and preferably are orthogonal and normalized, i.e., orthonormal. The term "orthogonal" denotes that, if the amplitude of a signal applied to one of the rows is multiplied by the amplitude of a signal applied to another one of the rows, the integral of this product over the frame period is zero. The term "normalized" denotes that all the row signals have the same rms voltage integrated over the frame period T. During each frame period a plurality of signals for the column electrodes are calculated and generated from the collective state of the pixels in each of the columns. The column voltage at any time t during the frame period is proportional to the sum obtained by considering each pixel in the column, multiplying a "pixel value" representing the optical state (either -1 for fully "on", +1 for fully "off", or values between -1 and +1 for proportionally corresponding gray shades) of the pixel by the value of that pixel's row signal at time t, and adding the products obtained thereby to the sum. If driven in the active addressing manner described above, it can be shown mathematically that there is applied to each pixel of the display an rms voltage averaged over the frame period, and that the rms voltage is proportional to the pixel value for the frame. The advantage of active addressing is that it restores high contrast to the displayed image because, instead of applying a single, high level selection pulse to each pixel during the frame period, active addressing applies a plurality of much lower level (2-5 times the rms voltage) selection pulses spread throughout the frame period. In addition, the much lower level of the selection pulses substantially reduces the probability of alignment instabilities. As a result, utilizing active addressing methods, rms-responding displays, such as LCDs used in laptop computers, can display image data at video speeds without smearing or flickering. Additionally, LCDs driven with active addressing methods can display image data having multiple shades without the contrast problems present in LCDs driven with conventional multiplexed addressing methods. A drawback to utilizing active addressing results from the large number of calculations required to generate column and row signals for driving an rms-responding display. For example, a gray scale display having 480 rows and 640 columns and a frame rate of 60 frames per second requires just under ten billion calculations per second. While it is, of course, possible to perform calculations at this rate, such complex, rapidly performed calculations necessitate a large amount of power consumption. In portable, battery powered devices, such as laptop computers and radio receivers, the power consumption issue is particularly important because battery life is a primary design consideration. Thus, what is needed is a method and apparatus for minimizing the power consumption required to display image data on an active-addressed display. Summary of the Invention According to an aspect of the present invention, a method for compressing data in an electronic device having an active-addressed display comprises the step of receiving image data. The method further comprises the step of compressing the image data in a two-dimensional transformation utilizing a plurality of orthogonal functions, thereby generating compressed data. Subsequently, a set of column values in accordance with active-addressing techniques is generated by performing a one-dimensional transformation of the compressed data utilizing the plurality of orthogonal functions. According to another aspect of the present invention, a method for compressing data subsequent to displaying the data in an electronic device having an active-addressed display comprises the steps of receiving image data and generating a set of column values in accordance with active addressing techniques by one-dimensionally transforming the image data utilizing a plurality of orthogonal functions. The method further comprises the step of driving columns of the active-addressed display with analog voltages corresponding to the set of column values. The image data is then compressed by using a compression method in which the set of column values is one-dimensionally transformed utilizing the plurality of orthogonal functions, wherein the compression method results in compressed data which is subsequently stored. According to still another aspect of the present invention, an electronic device for driving an active-addressed display comprises a data port for receiving image data and compressing circuitry coupled to the data port for generating compressed data by compressing the image data using a method in which the image data is two-dimensionally transformed utilizing a plurality of orthogonal functions. The electronic device further comprises transforming circuitry coupled to the compressing circuitry for performing a one-dimensional transformation of the compressed data utilizing the plurality of orthogonal functions to generate a set of column values. Column drivers coupled to the transforming circuitry and the active-addressed display drive columns of the active-addressed display with a first set of analog voltages corresponding to the set of column values. Brief Description of the Drawings FIG. 1 is a front orthographic view of a portion of a conventional liquid crystal display. FIG. 2 is an orthographic cross-section view along line 2-2 of FIG. 1 of the conventional liquid crystal display. FIG. 3 is a matrix of Walsh functions in accordance with the present invention. FIG. 4 depicts Walsh functions in accordance with the present invention. FIG. 5 is an electrical block diagram of an electronic device for generating signals to active-address the liquid crystal display of FIG. 1 in accordance with the present invention. FIG. 6 is a flowchart depicting the operation of a controller included in the electronic device of FIG. 5 in accordance with the present invention. Description of a Preferred Embodiment Referring to FIGs. 1 and 2, orthographic front and cross-section views of a portion of a conventional liquid crystal display (LCD) 100 depict first and second transparent substrates 102, 206 having a space therebetween filled with a layer of liquid crystal material 202. A perimeter seal 204 prevents the liquid crystal material from escaping from the LCD 100. The LCD 100 further includes a plurality of transparent electrodes comprising row electrodes 106 positioned on the second transparent substrate 206 and column electrodes 104 positioned on the first transparent substrate 102. At each point at which a column electrode 104 overlaps a row electrode 106, such as the overlap 108, voltages applied to the overlapping electrodes 104, 106 can control the optical state of the liquid crystal material 202 therebetween, thus forming a controllable picture element, hereafter referred to as a "pixel". While an LCD is the preferred display element in accordance with the preferred embodiment of the present invention, it will be appreciated that other types of display elements may be used as well, provided that such other types of display elements exhibit optical characteristics responsive to the square of the voltage applied to each pixel, similar to the root mean square (rms) response of an LCD. FIGs. 3 and 4 depict an eight-by-eight (third order) matrix of Walsh functions 300 and the corresponding Walsh waves 400 in accordance with the preferred embodiment of the present invention. Walsh functions are both orthogonal and normalized, i.e., orthonormal, and are therefore preferable for use in an active-addressed display system, as briefly discussed in the Background of the Invention herein above. It may be appreciated by one of ordinary skill in the art that other classes of functions, such as Pseudo Random Binary Sequence (PRBS) functions or Direct Cosine Transform (DCT) functions, may also be utilized in active- addressed display systems. When Walsh functions are used in an active-addressed display system, voltages having levels represented by the Walsh waves 400 are uniquely applied to a selected plurality of electrodes of the LCD 100. For example, the Walsh waves 404, 406, and 408 could be applied to the first (uppermost), second and third row electrodes 106, respectively, and so on. In this manner, each of the Walsh waves 400 would be applied uniquely to a corresponding one of the row electrodes 106. It is preferable not to use the Walsh wave 402 in an LCD application because the Walsh wave 402 would bias the LCD 100 with an undesirable DC voltage. It is of interest to note that the values of the Walsh waves 400 are constant during each time slot t. The duration of the time slot t for the eight Walsh waves 400 is one-eighth of the duration of one complete cycle of Walsh waves 400 from start 410 to finish 412. When using Walsh waves for actively addressing a display, the duration of one complete cycle of the Walsh waves 400 is set equal to the frame duration, i.e., the time to receive one complete set of data for controlling all the pixels 108 of the LCD 100. The eight Walsh waves 400 are capable of uniquely driving up to eight row electrodes 106 (seven if the Walsh wave 402 is not used). It will be appreciated that a practical display has many more rows. For example, displays having four-hundred-eight rows and six-hundred-forty columns are widely used today in laptop computers. Because Walsh function matrices are available in complete sets determined by powers of two, and because the orthonormality requirement for active addressing does not allow more than one electrode to be driven from each Walsh wave, a five- hundred-twelve by five-hundred-twelve (2 9 x 2 9 ) Walsh function matrix would be required to drive a display having four-hundred-eighty row electrodes 106. For this case, the duration of the time slot t is 1/512 of the frame duration. Four-hundred-eight Walsh waves would be used to drive the four-hundred-eighty row electrodes 106, while the remaining thirty- two, preferably including the first Walsh wave 402 having a DC bias, would be unused. It will be appreciated that driving a display, such as the LCD 100 (FIG. 1), in accordance with the active-addressing technique as described above involves a large number of calculations that must be rapidly performed, thereby necessitating a large amount of power consumption. In portable devices which are battery powered, the power consumption is a very important issue because of the limited capacity of the battery. Referring next to FIG. 5, an electrical block diagram of an electronic device 500 including an active-addressed display, such as the LCD 100, is shown. The electronic device 500, e.g., a portable laptop computer or a paging receiver, comprises a data port 505 for receiving image data from a video source (not shown). The data port 505 may be, for example, a communication bus, a floppy drive for reading image data from diskettes, or, in the case of a paging receiver, receiving circuitry for recovering image data from a radio frequency (RF) signal. The electronic device 500 further comprises an analog-to-digital (A/D) converter 510 for converting the analog image data values to digital image data values, which are provided to a controller 515 for transforming the image data into another domain, as will be explained in greater detail below. The resolution and range of the A/D converter 510 is determined by the desired image to be displayed on the LCD 100. For instance, if the pixels 108 of the LCD 100 are to be either fully "on" or fully "off", the A/D converter 510 may convert the image data to binary data, wherein -1 represents a fully on pixel and +1 represents a fully off pixel. If gray shades are also to be displayed on the LCD 100, the A/D converter 510 may generate values between -1 and +1 for the gray shades. It will be recognized that the A/D converter 510 may not be necessary if digital image data is received by the data port 505. Coupled to the controller 515 is an orthonormal function database 520 for storing a plurality of functions, which are orthogonal and preferably normalized, in the form of an orthonormal matrix, the number of rows of which are preferably greater than or equal to the number of rows included in the LCD 100. The orthonormal matrix may be, for example, the Walsh function matrix 300 (FIG. 3), although matrices of other orthonormal functions, such as DCT or PRBS functions, may be used as well. In accordance with the present invention, the orthonormal matrix is utilized by the controller 515 in transforming the image data upon reception. When the image data is received, the controller 515 performs a two-dimensional transformation of the image data utilizing the orthonormal matrix to result in two-dimensionally transformed image data. By way of example, the two-dimensional transformation can be accomplished utilizing a Fast Fourier Transform algorithm, or modification thereof, or a Fast Walsh Transform, although many other fast, efficient algorithms can be alternatively utilized. One such algorithm involves the use of matrix multiplication and can be represented by the following equation: I 2D = OM * I * OM, wherein ∑ 2D represents the two-dimensionally transformed image data, I represents the image data, and OM represents the orthonormal matrix stored in the orthonormal function database 520. It will be appreciated that, when matrix multiplication is utilized, the order of the terms in the above-recited equation cannot be varied. Further coupled to the controller 515 is a quantizer 525, which quantizes, in a conventional manner, the two-dimensionally transformed image data to a closest of a number of predetermined levels. An entropy encoder 530 coupled to the controller 515 is employed to compress the quantized data utilizing one of several well known entropy encoding schemes, such as Huffman coding, in which the values of the quantized data are encoded depending upon the probability of occurrence. According to the present invention, the electronic device 500 further includes a memory device, such as a random access memory (RAM) 535, for storing the compressed data. In this manner, image data received by the electronic device 500 is compressed prior to storage, thereby consuming less space in memory. The storage of compressed image data, rather than the image data itself, is especially advantageous when the electronic device 500 is a portable device, such as a laptop computer, because market trends have dictated that portable devices, which are often carried by a user, be designed as small and lightweight as possible. Therefore, with this goal in mind, the size of components, such as memory, included in a portable device is also limited. Preferably, the electronic device 500 further comprises, in addition to the RAM 535, a read only memory (ROM) 540, which stores subroutines executed by the controller 515 during operation of the electronic device 500, and a clock 545, which generates timing signals for use in system timing. Additionally, a data entry device 550 may be coupled to the controller 515. When the electronic device 500 is a laptop computer, for instance, the data entry device 550 may comprise a keyboard, whereas, when the electronic device 500 is a paging receiver, user-accessible controls, rather than a keyboard, may be coupled to the controller 515. In accordance with the present invention, the image data can be displayed automatically, or the data entry device 550 can be used to input commands directing the controller 515 to present the image data. When so directed, the controller 515 operates on the compressed data to generate signals suitable for active-addressing the LCD 100. More specifically, an entropy decoder 555 is employed to decode the compressed data, resulting in the two-dimensionally transformed image data which has been previously quantized. This data can be easily and quickly transformed into signals for active-addressing columns of the LCD 100 by performing a one- dimensional inverse transformation of the data. It will be appreciated by one of ordinary skill in the art that the calculations are further simplified when it is recognized that an orthonormal matrix, i.e., a separable and symmetric matrix, is equal to its inverse, i.e., OM = 1/OM. Therefore, because the orthonormal matrix stored in the orthonormal function database 520 was previously utilized in the data compression process, the same orthonormal matrix can be utilized by the controller 515 to perform a one-dimensional transformation, e.g., a Walsh Transform, rather than a one-dimensional inverse transformation. When matrix multiplication is used, this process is illustrated by the following equation: CV = IID = I2D * OM, wherein I 2 D is the two-dimensionally transformed image data that has been quantized, OM is the orthonormal matrix, and IID is the resulting one-dimensionally transformed image data, which is equivalent to column values (CV) suitable for active-addressing the columns of the LCD 100. As briefly described herein above in the Background of the Invention, the row signals for driving the rows of the LCD 100 are signals derived from orthonormal functions independent of the image data. The column signals, i.e., analog voltages corresponding to the column values, for driving the columns of the LCD 100 are linear combinations of all row signals and the image data and can be generated by one-dimensionally transforming the image data utilizing the orthonormal functions. Therefore, it will be appreciated that the column values generated by one- dimensionally transforming the quantized data are already in a form suitable for active-addressing the columns of the LCD. As a result, the electronic device 500 conveniently avoids having to decompress the stored data, which has been previously compressed for storage. The electronic device 500 further avoids the necessity of generating column values directly from the image data each time the image data is to be displayed. Instead, the electronic device 500 simply performs the one-dimensional transform on the compressed data when it is to be displayed. In conventional devices, on the other hand, data that is compressed and stored in memory must be decompressed, which involves complex calculations, before it can be displayed. Additionally, if a display in the device is to be active-addressed, the device also generates, in a conventional manner, the column signals for driving columns of the display. As a result, conventional devices must include a large amount of complex circuitry which requires a corresponding large amount of current for operation. Therefore, conventional methods for compression, decompression, and subsequent display of image data may not be suitable for use in portable devices, which are typically powered by a low capacity battery. One of ordinary skill in the art will recognize that the electronic device 500 according to the present invention exploits the similarities between data compression and active addressing to reduce the number and complexity of calculations for displaying compressed image data, thereby necessitating a smaller amount of power consumption than conventional devices. As a result, the battery life of the electronic device 500 may be longer than that of a battery powering a conventional device which displays compressed data utilizing active addressing techniques. As shown in FIG. 5, the electronic device 500 further comprises a digital-to-analog (D/A) converter 560 coupled to the controller 515 for converting the column values to analog voltages and column drivers 565 coupled to the D/A converter 560 for driving the columns of the LCD 100 with the analog voltages, i.e., column signals. Additionally, row drivers 570 are employed to drive the rows of the LCD 100 with analog voltages, i.e. row signals, corresponding to the orthonormal functions. The controller 515, the ROM 540, the RAM 535, and the clock 545 can be implemented by using a suitably programmed digital signal processor (DSP), such as the DSP 56000 manufactured by Motorola, Inc. of Schaumburg, Illinois, although other integrated or hard-wired circuitry that is capable of performing equivalent operations may be alternatively utilized. The A/D converter 510, the orthonormal function database 520, the entropy decoder 530, the entropy decoder 555, and the quantizer 525 can be implemented using an image compression /decompression chip, such as the model no. CL550-30 chip manufactured by C-Cube Microsystems of San Jose, California. Additionally, the D/A converter 560, the column drivers 565, and the row drivers 570 can be implemented using the following conventional elements: Element Model No. Manufacturer D/A converter 560 CXD1178Q Sony Corporation column drivers 565 SED1779D0A Seiko Epson Corp. row drivers 570 SED1704 Seiko Epson Corp. It will be recognized by one of ordinary skill in the art that, when gray scale or color images are to be displayed, the electronic device 500 may, when necessary, further include means for calculating rms correction factors, which are calculated for each column of image data. The rms correction factors, once calculated from the image data, could be stored in the RAM 535 as additional information associated with the compressed image data, recovered when the compressed image data is to be displayed, and added to the columns of a matrix formed from the column values. This process would yield a matrix of "corrected" column values, which would thereafter be provided to the column drivers 565 as described above. Circuits and techniques for performing rms correction factor calculations are taught in the U.S. Patent Application entitled "Method and Apparatus for Driving an Electronic Display", by Herold, Attorney's Docket No. PT00843U, which is assigned to the assignee hereof, and which is hereby incorporated by reference. FIG. 6 is a flowchart depicting the operation of the controller 515 (FIG. 5) in accordance with the present invention. As described above, when the image data is received, at step 605, from the A/D converter 510, the controller 515 performs, at step 610, a two-dimensional transformation of the image data utilizing the orthonormal functions stored in the orthonormal function database 520. The transformation may be performed, for example, by using matrix multiplication or by using a Fast Walsh Transform. Thereafter, the two-dimensionally transformed image data is provided, at step 615, to the quantizer 525 for processing thereby. Subsequent to receiving, at step 620, the quantized data, the controller 515 provides, at step 625, the quantized data to the entropy encoder 530. The entropy encoder 530 processes the quantized data to generate compressed image data, which is transmitted, at step 630, to the controller 515 for storage, at step 635, in the RAM 535. When the image is to be subsequently displayed, at step 640, the controller 515 retrieves, at step 645, the compressed data for transmission, at step 650, to the entropy decoder 555 (FIG. 5). The entropy decoder 555 decodes the compressed data to recover the quantized data, which is returned, at step 655, to the controller 515. Subsequently, the controller 515 performs, at step 660, a one-dimensional transformation of the quantized data utilizing the orthonormal functions, thereby generating one- dimensional transformed image data which is equivalent to the column values used for active addressing the columns of the LCD 100. The column values are, as described above, provided, at step 665, to the D/A converter 560, which subsequently provides analog column values to the column drivers 565. Additionally, the controller 515 provides, at step 670, the orthonormal functions to the row drivers 570. In accordance with active-addressing techniques, the column drivers 565 drive the columns of the LCD 100 and the row drivers 570 drive the rows of the LCD 100 at approximately the same time. In accordance with the present invention, further embodiments are envisioned in which the image defined by the image data is displayed by the LCD 100 prior to storage. In this situation, rather than compressing the image data using the two-dimensional transform upon reception, the image data is simply transformed in a one-dimensional transformation using the orthonormal functions stored in the orthonormal function database 520 (FIG. 5). The column values thus generated are used to drive columns of the LCD 100, and the orthonormal functions are used to drive rows of the LCD 100, as described above. Thereafter, if the image data is to be stored, the compression process is completed by performing a further one-dimensional transform of the column values to arrive at the two- dimensionally transformed data. Subsequent to quantization and entropy encoding, the resulting compressed data is stored, thereby consuming a lesser amount of space in the RAM 535. In summary, the electronic device as described above exploits the similarities between data compression and active-addressing techniques to reduce both the complexity of necessary circuitry and the number of calculations performed thereby, resulting in a smaller amount of power consumption by the electronic device. More specifically, the electronic device, upon receiving image data, compresses the image data in a two- dimensional transformation using orthonormal functions before storage of the image data. In this manner, the compressed data advantageously requires less storage space than would the image data itself. Thereafter, when the image data is to be displayed, the electronic device simply performs, after decoding the compressed data, a one-dimensional transformation of the compressed data utilizing the orthonormal functions, which results in column values which are already in a form suitable for active-addressing columns of an rms-responding display, such as an LCD. Because the electronic device avoids complex decompression calculations and subsequent complex column value calculations, the battery life of the electronic device is longer than that of a conventional device for compressing and subsequently displaying image data on an active-addressed display. It may be appreciated by now that there has been provided a method and apparatus which minimizes the power consumption required to display image data on an active-addressed display. What is claimed is:

Claims: CLAIMS 1. A method for compressing data in an electronic device having an active-addressed display, the method comprising the steps of: receiving image data; compressing the image data in a two-dimensional transformation utilizing a plurality of orthogonal functions, thereby generating compressed data; and subsequently generating a set of column values in accordance with active-addressing techniques by performing a one-dimensional transformation of the compressed data utilizing the plurality of orthogonal functions. 2. The method according to claim 1, further comprising the step of: driving columns of the active-addressed display with a first set of analog voltages corresponding to the set of column values. 3. The method according to claim 2, further comprising the step of: driving rows of the active-addressed display with a second set of analog voltages corresponding to the plurality of orthogonal functions. 4. The method according to claim 1, further comprising the step of: storing, subsequent to the compressing step, the compressed data. 5. The method according to claim 1, wherein the compressing step comprises the steps of: performing the two-dimensional transformation of the image data utilizing the plurality of orthogonal functions to generate two- dimensionally transformed image data; quantizing the two-dimensionally transformed image data to generate quantized data; and entropy encoding the quantized data to generate the compressed data. 6. The method according to claim 5, wherein the step of performing the two-dimensional transformation comprises the step of: performing a two-dimensional Walsh transformation of the image data to generate the two-dimensionally transformed image data. 7. The method according to claim 5, wherein the step of performing the two-dimensional transformation comprises the steps of: multiplying an orthogonal matrix representative of the plurality of orthogonal functions with an image matrix representative of the image data to form an intermediate matrix; and multiplying the intermediate matrix with the orthogonal matrix to form the two-dimensionally transformed image data. 8. The method according to claim 5, wherein the generating step comprises the steps of: entropy decoding the compressed data to recover the quantized data; and performing a one-dimensional transformation of the quantized data utilizing the plurality of orthogonal functions to generate the set of column values. 9. The method according to claim 8, wherein the step of performing the one-dimensional transformation comprises the step of: performing a one-dimensional Walsh transformation of the quantized data to generate the set of column values. 10. A method for compressing data subsequent to displaying the data in an electronic device having an active-addressed display, the method comprising the steps of: receiving image data; generating a set of column values in accordance with active addressing techniques by one-dimensionally transforming the image data utilizing a plurality of orthogonal functions; driving columns of the active-addressed display with analog voltages corresponding to the set of column values; compressing the image data by using a compression method in which the set of column values is one-dimensionally transformed utilizing the plurality of orthogonal functions, wherein the compression method results in compressed data; and storing the compressed data. 11. An electronic device for driving an active-addressed display, the electronic device comprising: receiving means for receiving image data; compressing means coupled to the receiving means for generating compressed data by compressing the image data using a method in which the image data is two-dimensionally transformed utilizing a plurality of orthogonal functions; transforming means coupled to the compressing means for performing a one-dimensional transformation of the compressed data utilizing the plurality of orthogonal functions to generate a set of column values; and column driving means coupled to the transforming means and the active-addressed display for driving columns of the active-addressed display with a first set of analog voltages corresponding to the set of column values. 12. The electronic device according to claim 11, further comprising: a memory for storing the compressed data. 13. The electronic device according to claim 11, further comprising: row driving means coupled to the compressing means and the active-addressed display for driving rows of the active-addressed display with a second set of analog voltages corresponding to the plurality of orthogonal functions. 14. The electronic device according to claim 11, wherein: the image data is two-dimensionally transformed utilizing a two-dimensional Walsh transform; and the one-dimensional transform of the compressed data is a one- dimensional Walsh transform. 15. The electronic device according to claim 11, wherein: the image data is two-dimensionally transformed utilizing matrix multiplication techniques; and the one-dimensional transform of the compressed data is performed utilizing matrix multiplication techniques. 16. The electronic device according to claim 11, wherein the column driving means comprises column drivers for driving the columns of the active-addressed display with the first set of analog voltages corresponding to the set of column values. 17. The electronic device according to claim 11, wherein the compressing means comprises: a database for storing the plurality of orthonormal functions; a controller coupled to the database for performing the two- dimensional transformation of the image data to generate two- dimensionally transformed image data; a quantizer coupled to the controller for quantizing the two- dimensionally transformed image data to generate quantized data; and an entropy encoder coupled to the quantizer for entropy encoding the quantized data to generate the compressed data. 18. The electronic device according to claim 17, wherein the transforming means comprises: an entropy decoder coupled to the entropy encoder and the controller for entropy decoding the compressed data to result in the quantized data; and the controller, wherein the controller further performs the one- dimensional transformation to generate the set of column values. 19. An electronic device for driving an active-addressed display, the electronic device comprising: a data port for receiving image data; a database coupled to the data port for storing a plurality of orthogonal functions; first transforming means coupled to the database and the data port for two-dimensionally transforming the image data utilizing the plurality of orthogonal functions to generate two-dimensionally transformed image data; a quantizer coupled to the first transforming means for quantizing the two-dimensionally transformed image data to generate quantized data; an entropy encoder coupled to the quantizer for entropy encoding the quantized data to generate compressed data; a memory coupled to the entropy encoder for storing the compressed data; an entropy decoder coupled to the memory for entropy decoding the compressed data to result in the quantized data; second transforming means coupled to the entropy decoder for one-dimensionally transforming the quantized data using the plurality of orthogonal functions to generate a set of column values; and column drivers coupled to the second transforming means for driving columns of the active-addressed display with a first set of analog voltages corresponding to the set of column values. 20. The electronic device according to claim 19, further comprising: row drivers coupled to the database and the active-addressed display for driving rows of the active-addressed display with a second set of analog voltages corresponding to the plurality of orthogonal functions.

Inventors: ORLEN NOAH PAUL, SAIDI ALI, ORLEN, NOAH, PAUL, SAIDI, ALI
Applicants: MOTOROLA INC, MOTOROLA, INC.
Application year: 1994
Main classification: G06K9
IPC codes: G02F1, G09G3, H04N1, H04N5, H04N7